Display apparatus and method of driving display panel using the same

ABSTRACT

A display apparatus configured to adjust a driving frequency of a display panel by including a driving controller configured to: determine a low driving frequency corresponding to input image data; determine a plurality of compensation frequencies greater than the low driving frequency; and insert a plurality of compensation frequency frames having the compensation frequencies prior to a low driving frequency frame having the low driving frequency in a low frequency driving mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/739,606, filed Jan. 10, 2020, which claims priority to and thebenefit of Korean Patent Application No. 10-2019-0004826, filed Jan. 14,2019, the entire content of both of which is incorporated herein byreference.

BACKGROUND 1. Field

Aspects of some example embodiments of the present inventive conceptrelate to a display apparatus and a method of driving a display panelusing the display apparatus.

2. Description of the Related Art

Generally, a display apparatus includes a display panel and a displaypanel driver. The display panel includes a plurality of gate lines, aplurality of data lines, a plurality of emission lines and a pluralityof pixels. The display panel driver includes a gate driver, a datadriver, an emission driver and a driving controller. The gate driveroutputs gate signals to the gate lines. The data driver outputs datavoltages to the data lines. The emission driver outputs emission signalsto the emission lines. The driving controller controls the gate driver,the data driver, and the emission driver.

When the display panel displays a static image or the display panel isoperated in Always On Mode, a driving frequency of the display panel maybe reduced to reduce the power consumption.

When the display panel displays the static image and the imagetransition occurs, an afterimage of the previous static image may begenerated or the flicker may be generated due to hysteresischaracteristics of pixel switching elements.

The above information disclosed in this Background section is only forenhancement of understanding of the background and therefore it maycontain information that does not constitute prior art.

SUMMARY

Aspects of some example embodiments of the present inventive conceptrelate to a display apparatus and a method of driving a display panelusing the display apparatus. For example, some example embodiments ofthe present inventive concept relate to a display apparatus that may becapable of reducing power consumption and enhancing a display qualityand a method of driving a display panel using the display apparatus.

Some example embodiments of the present inventive concept provide adisplay apparatus capable of reducing a power consumption of a displayapparatus and enhancing a display quality of a display panel.

Some example embodiments of the present inventive concept also provide amethod of driving a display panel using the display apparatus.

According to some example embodiments of the present invention concept,a display apparatus includes a display panel, a gate driver, a datadriver, an emission driver and a driving controller. The display panelincludes a pixel comprising a switching element of a first type and aswitching element of a second type different from the first type. Thegate driver is configured to output a gate signal to the display panel.The data driver is configured to output a data voltage to the displaypanel. The emission driver is configured to output an emission signal tothe display panel. The driving controller is configured to determine alow driving frequency corresponding to input image data, to determine aplurality of compensation frequencies greater than the low drivingfrequency, and to insert a plurality of compensation frequency frameshaving the compensation frequencies prior to a low driving frequencyframe having the low driving frequency in a low frequency driving mode.

According to some example embodiments, the switching element of thesecond type may be driven in the low driving frequency and the switchingelement of the first type may be driven in a first driving frequencygreater than the low driving frequency in the low frequency drivingmode.

According to some example embodiments, the switching element of thefirst type and the switching element of the second type may be driven ina normal driving frequency in a normal driving mode.

According to some example embodiments, the first driving frequency maybe the normal driving frequency.

According to some example embodiments, the driving controller may beconfigured to determine a first compensation frequency and a secondcompensation frequency. The first compensation frequency may be a normaldriving frequency of a normal driving mode. The second compensationfrequency may be less than the normal driving frequency and greater thanthe low driving frequency.

According to some example embodiments, the driving controller may beconfigured to determine a first compensation frequency and a secondcompensation frequency less than the first compensation frequency. Afirst compensation frequency frame having the first compensationfrequency may be inserted prior to a second compensation frequency framehaving the second compensation frequency.

According to some example embodiments, the driving controller may beconfigured to determine a first compensation frequency and a secondcompensation frequency less than the first compensation frequency. Aplurality of first compensation frequency frames having the firstcompensation frequency may be inserted. A plurality of secondcompensation frequency frames having the second compensation frequencymay be inserted.

According to some example embodiments, the compensation frequency frameshaving at least two compensation frequencies may be repetitivelyinserted until a predetermined count is satisfied.

According to some example embodiments, the compensation frequency frameshaving at least two compensation frequencies may be repetitivelyinserted until a predetermined condition is satisfied.

According to some example embodiments, the driving controller may beconfigured to insert the compensation frequency frames when an imagetransition of the input image data occurs from a first static image to asecond static image different from the first static image.

According to some example embodiments, the driving controller may beconfigured to generate the compensation frequencies by repetitivelydividing a normal driving frequency of a normal driving mode by aparameter.

According to some example embodiments, the driving controller may beconfigured to determine the normal driving frequency as a firstcompensation frequency. The driving controller may be configured todetermine a second compensation frequency by dividing the normal drivingfrequency by the parameter when the second compensation frequency isgreater than the low driving frequency. The driving controller may beconfigured to determine a third compensation frequency by dividing thesecond driving frequency by the parameter when the third compensationfrequency is greater than the low driving frequency.

According to some example embodiments, the driving controller may beconfigured to generate the compensation frequencies by repetitivelymultiplying a parameter to the low driving frequency.

According to some example embodiments, the driving controller may beconfigured to determine an N-th compensation frequency by multiplyingthe parameter to the low driving frequency when the N-th compensationfrequency is less than a normal driving frequency of a normal drivingmode. The driving controller may be configured to determine a (N−1)-thcompensation frequency by multiplying the parameter to the N-thcompensation frequency when the (N−1)-th compensation frequency is lessthan the normal driving frequency. N is a natural number equal to orgreater than two.

According to some example embodiments, the switching element of thefirst type may be a polysilicon thin film transistor. The switchingelement of the second type may be an oxide thin film transistor.

According to some example embodiments, the switching element of thefirst type may be a P-type transistor. The switching element of thesecond type may be an N-type transistor.

According to some example embodiments, the pixel may include a firstpixel switching element comprising a control electrode connected to afirst node, an input electrode connected to a second node and an outputelectrode connected to a third node, a second pixel switching elementcomprising a control electrode to which a first data write gate signalis applied, an input electrode to which the data voltage is applied andan output electrode connected to the second node, a third pixelswitching element comprising a control electrode to which a second datawrite gate signal is applied, an input electrode connected to the firstnode and an output electrode connected to the third node, a fourth pixelswitching element comprising a control electrode to which a datainitialization gate signal is applied, an input electrode to which aninitialization voltage is applied and an output electrode connected tothe first node, a fifth pixel switching element comprising a controlelectrode to which the emission signal is applied, an input electrode towhich a high power voltage is applied and an output electrode connectedto the second node, a sixth pixel switching element comprising a controlelectrode to which the emission signal is applied, an input electrodeconnected to the third node and an output electrode connected to ananode electrode of an organic light emitting element, a seventh pixelswitching element comprising a control electrode to which an organiclight emitting element initialization gate signal is applied, an inputelectrode to which the initialization voltage is applied and an outputelectrode connected to the anode electrode of the organic light emittingelement, a storage capacitor comprising a first electrode to which thehigh power voltage is applied and a second electrode connected to thefirst node and the organic light emitting element comprising the anodeelectrode connected to the output electrode of the sixth switchingelement and a cathode electrode to which a low power voltage is applied.

According to some example embodiments, the first pixel switchingelement, the second pixel switching element, the fifth pixel switchingelement and the sixth pixel switching element may be the polysiliconthin film transistors. The third pixel switching element, the fourthpixel switching element and the seventh pixel switching element may bethe oxide thin film transistors.

According to some example embodiments, the first pixel switchingelement, the second pixel switching element, the fifth pixel switchingelement, the sixth pixel switching element and the seventh pixelswitching element may be the polysilicon thin film transistors. Thethird pixel switching element and the fourth pixel switching element maybe the oxide thin film transistors.

According to some example embodiments of the present inventive concept,in a method of driving a display panel, the method includes determininga low driving frequency corresponding to input image data in a lowfrequency driving mode, determining a plurality of compensationfrequencies greater than the low driving frequency in the low frequencydriving mode, outputting a gate signal to the display panel comprising apixel comprising a switching element of a first type and a switchingelement of a second type different from the first type based on the lowdriving frequency and the compensation frequencies, outputting a datavoltage to the display panel and outputting an emission signal to thedisplay panel. A plurality of compensation frequency frames having thecompensation frequencies is inserted prior to a low driving frequencyframe having the low driving frequency in the low frequency drivingmode.

According to some example embodiments, in a display apparatus and amethod of driving the display panel, a plurality of compensationfrequency frames may be inserted prior to a low driving frequency framein a low frequency driving mode so that instances of an afterimage ofthe previous image or the flicker due to the hysteresis characteristicsof the pixel switching elements may be prevented or reduced.

According to some example embodiments, instances of flicker of thedisplay panel may be prevented or reduced in the low frequency drivingmode so that the power consumption of the display apparatus may bereduced and the display quality of the display panel may be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and characteristics of the presentinventive concept will become more apparent by describing aspects ofsome example embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a block diagram illustrating a display apparatus according tosome example embodiments of the present inventive concept;

FIG. 2 is a circuit diagram illustrating a pixel of a display panel ofFIG. 1 ;

FIG. 3 is a timing diagram illustrating input signals applied to thepixel of FIG. 2 ;

FIG. 4 is a timing diagram illustrating input signals applied to thepixels of the display panel of FIG. 2 in a low frequency driving mode;

FIG. 5 is a flowchart diagram illustrating a method of driving thedisplay panel of FIG. 1 when a low driving frequency is 1 Hz;

FIG. 6 is a flowchart diagram illustrating a method of driving thedisplay panel of FIG. 1 when a low driving frequency is 2 Hz;

FIG. 7 is a table illustrating compensation frequencies for driving thedisplay panel of FIG. 1 ;

FIGS. 8A and 8B are flowchart diagrams illustrating a method of drivingthe display panel of FIG. 1 ;

FIG. 9 is a timing diagram illustrating compensation frequency frames ofthe display panel of FIG. 1 ;

FIG. 10 is a table illustrating compensation frequencies for driving adisplay panel according to some example embodiments of the presentinventive concept;

FIG. 11 is a flowchart diagram illustrating a method of driving thedisplay panel of FIG. 10 ;

FIG. 12 is a flowchart diagram illustrating a method of driving adisplay panel according to some example embodiments of the presentinventive concept when a low driving frequency is 1 Hz;

FIG. 13 is a flowchart diagram illustrating a method of driving adisplay panel according to some example embodiments of the presentinventive concept when a low driving frequency is 1 Hz;

FIG. 14 is a circuit diagram illustrating a pixel of a display panelaccording to some example embodiments of the present inventive concept;and

FIG. 15 is a timing diagram illustrating input signals applied to thepixel of FIG. 14 .

DETAILED DESCRIPTION

Hereinafter, aspects of some example embodiments of the presentinventive concept will be explained in more detail with reference to theaccompanying drawings.

FIG. 1 is a block diagram illustrating a display apparatus according tosome example embodiments of the present inventive concept.

Referring to FIG. 1 , the display apparatus includes a display panel 100and a display panel driver. The display panel driver includes a drivingcontroller 200, a gate driver 300, a gamma reference voltage generator400, a data driver 500, and an emission driver 600.

The display panel 100 has a display region on which an image isdisplayed and a peripheral region adjacent to the display region.

The display panel 100 includes a plurality of gate lines GWPL, GWNL, GILand GBL, a plurality of data lines DL, a plurality of emission lines EL,and a plurality of pixels electrically connected to the gate lines GWPL,GWNL, GIL, and GBL, the data lines DL and the emission lines EL. Thegate lines GWPL, GWNL, GIL, and GBL may extend in a first direction D1,the data lines DL may extend in a second direction D2 crossing the firstdirection D1, and the emission lines EL may extend in the firstdirection D1.

The driving controller 200 receives input image data IMG and an inputcontrol signal CONT from an external apparatus. For example, the inputimage data IMG may include red image data, green image data, and blueimage data. The input image data IMG may include white image data. Theinput image data IMG may include magenta image data, cyan image data,and yellow image data. The input control signal CONT may include amaster clock signal and a data enable signal. The input control signalCONT may further include a vertical synchronizing signal and ahorizontal synchronizing signal.

The driving controller 200 generates a first control signal CONT1, asecond control signal CONT2, a third control signal CONT3, a fourthcontrol signal CONT4, and a data signal DATA based on the input imagedata IMG and the input control signal CONT.

The driving controller 200 generates the first control signal CONT1 forcontrolling an operation of the gate driver 300 based on the inputcontrol signal CONT, and outputs the first control signal CONT1 to thegate driver 300. The first control signal CONT1 may include a verticalstart signal and a gate clock signal.

The driving controller 200 generates the second control signal CONT2 forcontrolling an operation of the data driver 500 based on the inputcontrol signal CONT, and outputs the second control signal CONT2 to thedata driver 500. The second control signal CONT2 may include ahorizontal start signal and a load signal.

The driving controller 200 generates the data signal DATA based on theinput image data IMG. The driving controller 200 outputs the data signalDATA to the data driver 500.

The driving controller 200 generates the third control signal CONT3 forcontrolling an operation of the gamma reference voltage generator 400based on the input control signal CONT, and outputs the third controlsignal CONT3 to the gamma reference voltage generator 400.

The driving controller 200 generates the fourth control signal CONT4 forcontrolling an operation of the emission driver 600 based on the inputcontrol signal CONT, and outputs the fourth control signal CONT4 to theemission driver 600.

The gate driver 300 generates gate signals driving the gate lines GWPL,GWNL, GIL and GBL in response to the first control signal CONT1 receivedfrom the driving controller 200. The gate driver 300 may sequentiallyoutput the gate signals to the gate lines GWPL, GWNL, GIL, and GBL.

The gamma reference voltage generator 400 generates a gamma referencevoltage VGREF in response to the third control signal CONT3 receivedfrom the driving controller 200. The gamma reference voltage generator400 provides the gamma reference voltage VGREF to the data driver 500.The gamma reference voltage VGREF has a value corresponding to a levelof the data signal DATA.

According to some example embodiments, the gamma reference voltagegenerator 400 may be located in the driving controller 200, or in thedata driver 500.

The data driver 500 receives the second control signal CONT2 and thedata signal DATA from the driving controller 200, and receives the gammareference voltages VGREF from the gamma reference voltage generator 400.The data driver 500 converts the data signal DATA into data voltageshaving an analog type using the gamma reference voltages VGREF. The datadriver 500 outputs the data voltages to the data lines DL.

The emission driver 600 generates emission signals to drive the emissionlines EL in response to the fourth control signal CONT4 received fromthe driving controller 200. The emission driver 600 may output theemission signals to the emission lines EL.

FIG. 2 is a circuit diagram illustrating a pixel of the display panel100 of FIG. 1 . FIG. 3 is a timing diagram illustrating input signalsapplied to the pixel of FIG. 2 .

Referring to FIGS. 1 to 3 , the display panel 100 includes the pluralityof the pixels. Each pixel includes an organic light emitting elementOLED.

The pixel receives a data write gate signal GWP and GWN, a datainitialization gate signal GI, an organic light emitting elementinitialization signal GB, the data voltage VDATA and the emission signalEM and the organic light emitting element OLED of the pixel emits lightcorresponding to the level of the data voltage VDATA to display theimage.

According to some example embodiments, the pixel may include a switchingelement of a first type and a switching element of a second typedifferent from the first type. For example, the switching element of thefirst type may be a polysilicon thin film transistor. For example, theswitching element of the first type may be a low temperature polysilicon(LTPS) thin film transistor. For example, the switching element of thesecond type may be an oxide thin film transistor. For example, theswitching element of the first type may be a P-type transistor and theswitching element of the second type may be an N-type transistor.

For example, the data write gate signal may include a first data writegate signal GWP and a second data write gate signal GWN. The first datawrite gate signal GWP may be applied to the P-type transistor so thatthe first data write gate signal GWP has an activation signal of a lowlevel corresponding to a data writing timing. The second data write gatesignal GWN may be applied to the N-type transistor so that the seconddata write gate signal GWN has an activation signal of a high levelcorresponding to the data writing timing.

At least one of the pixels may include first to seventh pixel switchingelements T1 to T7, a storage capacitor CST and the organic lightemitting element OLED.

The first pixel switching element T1 includes a control electrodeconnected to a first node N1, an input electrode connected to a secondnode N2 and an output electrode connected to a third node N3.

For example, the first pixel switching element T1 may be the polysiliconthin film transistor. For example, the first pixel switching element T1may be the P-type thin film transistor. The control electrode of thefirst pixel switching element T1 may be a gate electrode, the inputelectrode of the first pixel switching element T1 may be a sourceelectrode and the output electrode of the first pixel switching elementT1 may be a drain electrode.

The second pixel switching element T2 includes a control electrode towhich the first data write gate signal GWP is applied, an inputelectrode to which the data voltage VDATA is applied and an outputelectrode connected to the second node N2.

For example, the second pixel switching element T2 may be thepolysilicon thin film transistor. For example, the second pixelswitching element T2 may be the P-type thin film transistor. The controlelectrode of the second pixel switching element T2 may be a gateelectrode, the input electrode of the second pixel switching element T2may be a source electrode and the output electrode of the second pixelswitching element T2 may be a drain electrode.

The third pixel switching element T3 includes a control electrode towhich the second data write gate signal GWN is applied, an inputelectrode connected to the first node N1 and an output electrodeconnected to the third node N3.

For example, the third pixel switching element T3 may be the oxide thinfilm transistor. For example, the third pixel switching element T3 maybe the N-type thin film transistor. The control electrode of the thirdpixel switching element T3 may be a gate electrode, the input electrodeof the third pixel switching element T3 may be a source electrode andthe output electrode of the third pixel switching element T3 may be adrain electrode.

The fourth pixel switching element T4 includes a control electrode towhich the data initialization gate signal GI is applied, an inputelectrode to which an initialization voltage VI is applied and an outputelectrode connected to the first node N1.

For example, the fourth pixel switching element T4 may be the oxide thinfilm transistor. For example, the fourth pixel switching element T4 maybe the N-type thin film transistor. The control electrode of the fourthpixel switching element T4 may be a gate electrode, the input electrodeof the fourth pixel switching element T4 may be a source electrode andthe output electrode of the fourth pixel switching element T4 may be adrain electrode.

The fifth pixel switching element T5 includes a control electrode towhich the emission signal EM is applied, an input electrode to which ahigh power voltage ELVDD is applied and an output electrode connected tothe second node N2.

For example, the fifth pixel switching element T5 may be the polysiliconthin film transistor. For example, the fifth pixel switching element T5may be the P-type thin film transistor. The control electrode of thefifth pixel switching element T5 may be a gate electrode, the inputelectrode of the fifth pixel switching element T5 may be a sourceelectrode and the output electrode of the fifth pixel switching elementT5 may be a drain electrode.

The sixth pixel switching element T6 includes a control electrode towhich the emission signal EM is applied, an input electrode connected tothe third node N3 and an output electrode connected to an anodeelectrode of the organic light emitting element OLED.

For example, the sixth pixel switching element T6 may be the polysiliconthin film transistor. For example, the sixth pixel switching element T6may be a P-type thin film transistor. The control electrode of the sixthpixel switching element T6 may be a gate electrode, the input electrodeof the sixth pixel switching element T6 may be a source electrode andthe output electrode of the sixth pixel switching element T6 may be adrain electrode.

The seventh pixel switching element T7 includes a control electrode towhich the organic light emitting element initialization gate signal GBis applied, an input electrode to which the initialization voltage VI isapplied and an output electrode connected to the anode electrode of theorganic light emitting element OLED.

For example, the seventh pixel switching element T7 may be the oxidethin film transistor. For example, the seventh pixel switching elementT7 may be the N-type thin film transistor. The control electrode of theseventh pixel switching element T7 may be a gate electrode, the inputelectrode of the seventh pixel switching element T7 may be a sourceelectrode and the output electrode of the seventh pixel switchingelement T7 may be a drain electrode.

The storage capacitor CST includes a first electrode to which the highpower voltage ELVDD is applied and a second electrode connected to thefirst node N1.

The organic light emitting element OLED includes the anode electrode anda cathode electrode to which a low power voltage ELVSS is applied.

In FIG. 3 , during a first duration DU1, the first node N1 and thestorage capacitor CST are initialized in response to the datainitialization gate signal GI. During a second duration DU2, a thresholdvoltage |VTH| of the first pixel switching element T1 is compensated andthe data voltage VDATA of which the threshold voltage |VTH| iscompensated is written to the first node N1 in response to the first andsecond data write gate signals GWP and GWN. During a third duration DU3,the anode electrode of the organic light emitting element OLED isinitialized in response to the organic light emitting elementinitialization gate signal GB. During a fourth duration DU4, the organiclight emitting element OLED emit the light in response to the emissionsignal EM so that the display panel 100 displays the image.

Although an emission off duration of the emission signal EM correspondsto first to third durations DU1, DU2, and DU3 according to some exampleembodiments, embodiments of the present inventive concept is not limitedthereto. The emission off duration of the emission signal EM may be setto include the data writing duration DU2. The emission off duration ofthe emission signal EM may be longer than a sum of the first to thirddurations DU1, DU2, and DU3.

During the first duration DU1, the data initialization gate signal GImay have an active level. For example, the active level of the datainitialization gate signal GI may be a high level. When the datainitialization gate signal GI has the active level, the fourth pixelswitching element T4 is turned on so that the initialization voltage VImay be applied to the first node N1. The data initialization gate signalGI[N] of a present stage may be generated based on a scan signalSCAN[N−1] of a previous stage.

During the second duration DU2, the first data write gate signal GWP andthe second data write gate signal GWN may have an active level. Forexample, the active level of the first data write gate signal GWP may bea low level and the active level of the second data write gate signalGWN may be a high level. When the first data write gate signal GWP andthe second data writhe gate signal GWN have the active level, the secondpixel switching element T2 and the third pixel switching element T3 areturned on. In addition, the first pixel switching element T1 is turnedon in response to the initialization voltage VI. The first data writegate signal GWP[N] of the present stage may be generated based on a scansignal SCAN[N] of the present stage. The second data write gate signalGWN[N] of the present stage may be generated based on the scan signalSCAN[N] of the present stage.

A voltage which is subtraction an absolute value |VTH| of the thresholdvoltage of the first pixel switching element T1 from the data voltageVDATA may be charged at the first node N1 along a path generated by thefirst to third pixel switching elements T1, T2 and T3.

During the third duration DU3, the organic light emitting elementinitialization signal GB may have an active level. For example, theactive level of the organic light emitting element initialization signalGB may be a high level. When the organic light emitting elementinitialization signal GB has the active level, the seventh pixelswitching element T7 is turned on so that the initialization voltage VImay be applied to the anode electrode of the organic light emittingelement OLED. The organic light emitting element initialization signalGB[N] of the present stage may be generated based on a scan signalSCAN[N+1] of a next stage.

During the fourth duration DU4, the emission signal EM may have anactive level. The active level of the emission signal EM may be a lowlevel. When the emission signal EM has the active level, the fifth pixelswitching element T5 and the sixth pixel switching element T6 are turnedon. In addition, the first pixel switching element T1 is turned on bythe data voltage VDATA.

A driving current flows through the fifth pixel switching element T5,the first pixel switching element T1 and the sixth pixel switchingelement T6 to drive the organic light emitting element OLED. Anintensity of the driving current may be determined by the level of thedata voltage VDATA. A luminance of the organic light emitting elementOLED is determined by the intensity of the driving current. The drivingcurrent ISD flowing through a path from the input electrode to theoutput electrode of the first pixel switching element T1 is determinedaccording to the following Equation 1.

$\begin{matrix}{{ISD} = {\frac{1}{2}\mu{Cox}\frac{W}{L}\left( {{VSG} - {❘{VTH}❘}} \right)^{2}}} & {{Equation}1}\end{matrix}$

In Equation 1, μ is a mobility of the first pixel switching element T1.Cox is a capacitance per unit area of the first pixel switching elementT1. W/L is a width to length ratio of the first pixel switching elementT1. VSG is a voltage between the input electrode N2 of the first pixelswitching element T1 and the control node N1 of the first pixelswitching element T1. |VTH| is the threshold voltage of the first pixelswitching element T1.

The voltage VG of the first node N1 after the compensation of thethreshold voltage |VTH| during the second duration DU2 may berepresented according to the following Equation 2.VG=VDATA−|VTH|  Equation 2

When the organic light emitting element OLED emits the light during thefourth duration DU4, the driving voltage VOV and the driving current ISDmay be represented according to the following Equations 3 and 4. InEquation 3, VS is a voltage of the second node N2.

$\begin{matrix}{{VOV} = {{{VS} - {VG} - {❘{VTH}❘}} = {{{ELVDD} - \left( {{VDATA} - {❘{VTH}❘}} \right) - {❘{VTH}❘}} = {{ELVDD} - {VDATA}}}}} & {{Equation}3}\end{matrix}$ $\begin{matrix}{{ISD} = {\frac{1}{2}\mu{Cox}\frac{W}{L}\left( {{ELVDD} - {VDATA}} \right)^{2}}} & {{Equation}4}\end{matrix}$

The threshold voltage |VTH| is compensated during the second durationDU2, so that the driving current ISD may be determined regardless of thethreshold voltage |VTH| of the first pixel switching element T1 when theorganic light emitting element OLED emits the light during the fourthduration DU4.

According to some example embodiments, when the image displayed on thedisplay panel 100 is a static image or the display panel is operated inAlways On Mode, a driving frequency of the display panel 100 may bedecreased to reduce power consumption. When all of the switchingelements of the pixel of the display panel 100 are polysilicon thin filmtransistor, a flicker may be generated due to a leakage current of thepixel switching element in the low frequency driving mode. Thus, some ofthe pixel switching elements may be designed using the oxide thin filmtransistors. According to some example embodiments, the third pixelswitching element T3, the fourth pixel switching element T4 and theseventh pixel switching element T7 may be the oxide thin filmtransistors. The first pixel switching element T1, the second pixelswitching element T2, the fifth pixel switching element T5 and the sixthpixel switching element T6 may be the polysilicon thin film transistors.

FIG. 4 is a timing diagram illustrating input signals applied to thepixels of the display panel of FIG. 2 in a low frequency driving mode.

Referring to FIGS. 1 to 4 , the display panel 100 may be driven in anormal driving mode in which the display panel 100 is driven in a normaldriving frequency and in a low frequency driving mode in which thedisplay panel 100 is driven in a frequency less than the normal drivingfrequency.

For example, when the input image data represent a video image, thedisplay panel 100 may be driven in the normal driving mode. For example,when the input image data represent a static image, the display panelmay be driven in the low frequency driving mode. For example, when thedisplay apparatus is operated in the always on mode, the display panelmay be driven in the low frequency driving mode.

The display panel 100 may be driven in a unit of frame. The displaypanel 100 may be refreshed in every frame in the normal driving mode.Thus, the normal driving mode includes only writing frames in which thedata is written in the pixel.

The display panel 100 may be refreshed in the frequency of the lowfrequency driving mode in the low frequency driving mode. Thus, the lowfrequency driving mode includes the writing frames in which the data iswritten in the pixel and holding frames in which the written data ismaintained without writing the data in the pixel.

For example, when the frequency of the normal driving mode is 60 Hz andthe frequency of the low frequency driving mode is 1 Hz, the lowfrequency driving mode includes one writing frame WRITE and fifty nineholding frames HOLD in a second. For example, when the frequency of thenormal driving mode is 60 Hz and the frequency of the low frequencydriving mode is 1 Hz, fifty nine continuous holding frames HOLD arelocated between two adjacent writing frames WRITE.

For example, when the frequency of the normal driving mode is 60 Hz andthe frequency of the low frequency driving mode is 10 Hz, the lowfrequency driving mode includes ten writing frame WRITE and fiftyholding frames HOLD in a second. For example, when the frequency of thenormal driving mode is 60 Hz and the frequency of the low frequencydriving mode is 10 Hz, five continuous holding frames HOLD are locatedbetween two adjacent writing frames WRITE.

According to some example embodiments, the second data write gate signalGWN and the data initialization gate signal GI may have a firstfrequency in the low frequency driving mode. The first frequency may bethe frequency of the low frequency driving mode. In contrast, the firstdata write gate signal GWP, the emission signal EM and the organic lightemitting element initialization gate signal GB may have a secondfrequency greater than the first frequency. The second frequency may bethe normal frequency of the normal driving mode. In FIG. 4 , the firstfrequency is 1 Hz and the second frequency is 60 Hz.

The emission signal EM in the frame may include an emission off durationOD when the emission signal EM has the inactive level and an emission onduration when the emission signal EM has the active level.

FIG. 5 is a flowchart diagram illustrating a method of driving thedisplay panel 100 of FIG. 1 when a low driving frequency is 1 Hz. FIG. 6is a flowchart diagram illustrating a method of driving the displaypanel 100 of FIG. 1 when a low driving frequency is 2 Hz.

Referring to FIGS. 1 to 6 , the driving controller 200 may determine thelow driving frequency corresponding to the input image data IMG in thelow frequency driving mode. The low driving frequency may be determinedbased on a degree of the flicker.

For example, when the flicker does not occur in the driving frequency of1 Hz, the low driving frequency may be determined to be 1 Hz.

For example, when the flicker occurs in the driving frequency of 1 Hzand the flicker does not occur in the driving frequency of 2 Hz, the lowdriving frequency may be determined to be 2 Hz.

The driving controller 200 may determine a plurality of compensationfrequencies greater than the low driving frequency. The drivingcontroller 200 inserts a plurality of compensation frequency frameshaving the compensation frequencies prior to a low driving frequencyframe having the low driving frequency.

In the low frequency driving mode, the switching element of the secondtype may be driven in the low driving frequency. In contrast, theswitching element of the first type may be driven in a first drivingfrequency greater than the low driving frequency. The first drivingfrequency may be the normal driving frequency of the normal drivingmode.

In the normal driving mode, both of the switching element of the firsttype and the switching element of the second type may be driven in thenormal driving frequency.

For example, when the image transition of the input image data IMG isoccurs from a first static image (Static Image A) to a second staticimage (Static Image B) different from the first static image (StaticImage A), the driving controller 200 may insert the compensationfrequency frames.

In FIG. 5 , the low driving frequency corresponding to the first staticimage (Static Image A) may be 1 Hz and the low driving frequencycorresponding to the second static image (Static Image B) may be 1 Hz.

For example, a first compensation frequency to compensate the flickermay be the normal driving frequency (e.g. 60 Hz). The normal drivingfrequency may mean an input frequency of the input image data IMG. Rightafter the image transition occurs from the first static image to thesecond static image different from the first static image, the displaypanel 100 may be driven in the first compensation frequency (e.g., 60Hz).

A second compensation frequency (e.g., 30 Hz) to compensate the flickermay be less than the first compensation frequency (e.g., 60 Hz) andgreater than the low driving frequency (e.g., 1 Hz) of the second staticimage. After the image transition occurs from the first static image tothe second static image and the display panel 100 is driven in the firstcompensation frequency (e.g., 60 Hz), the display panel 100 may bedriven in the second compensation frequency (e.g., 30 Hz).

The compensation frequencies after the second compensation frequency maybe generated in a predetermined rule. When the compensation frequencygenerated in the predetermined rule is less than the low drivingfrequency (e.g., 1 Hz), the compensation frequency may not be generated.In FIG. 5 , compensation frequencies may be generated by dividingprevious compensation frequencies by two. After the display panel 100 isdriven in the compensation frequency of 1.875 Hz, a subsequent candidatecompensation frequency may be determined to be 0.9375 Hz. 0.9375 Hz isless than the low driving frequency (e.g., 1 Hz), so that 0.9375 Hz isnot decided as the compensation frequency.

In FIG. 6 , the low driving frequency corresponding to the first staticimage (Static Image A) may be 1 Hz and the low driving frequencycorresponding to the second static image (Static Image B) may be 2 Hz.

For example, a first compensation frequency to compensate the flickermay be the normal driving frequency (e.g., 60 Hz). The normal drivingfrequency may mean an input frequency of the input image data IMG. Rightafter the image transition occurs from the first static image to thesecond static image different from the first static image, the displaypanel 100 may be driven in the first compensation frequency (e.g. 60Hz).

A second compensation frequency (e.g., 30 Hz) to compensate the flickermay be less than the first compensation frequency (e.g., 60 Hz) andgreater than the low driving frequency (e.g., 2 Hz) of the second staticimage. After the image transition occurs from the first static image tothe second static image and the display panel 100 is driven in the firstcompensation frequency (e.g., 60 Hz), the display panel 100 may bedriven in the second compensation frequency (e.g., 30 Hz).

The compensation frequencies after the second compensation frequency maybe generated according to a predetermined rule. When the compensationfrequency generated in the predetermined rule is less than the lowdriving frequency (e.g., 1 Hz), the compensation frequency may not begenerated. In FIG. 6 , compensation frequencies may be generated bydividing previous compensation frequencies by two. After the displaypanel 100 is driven in the compensation frequency of 3.75 Hz, asubsequent candidate compensation frequency may be determined to be1.875 Hz. 1.875 Hz is less than the low driving frequency (e.g., 2 Hz),so that 1.875 Hz is not decided as the compensation frequency.

FIG. 7 is a table illustrating compensation frequencies for driving thedisplay panel 100 of FIG. 1 . FIGS. 8A and 8B are flowchart diagramsillustrating a method of driving the display panel 100 of FIG. 1 . FIG.9 is a timing diagram illustrating the compensation frequency frames ofthe display panel 100 of FIG. 1 .

Referring to FIGS. 1 to 9 , the driving controller 200 may generate thecompensation frequencies by repetitively dividing the normal drivingfrequency of the normal driving mode by a parameter.

In FIG. 7 , the normal driving frequency may be 60 Hz and the parametermay be two. The first compensation frequency may be the normal drivingfrequency. The second compensation frequency may be 30 Hz which isgenerated by dividing the normal driving frequency by two. The secondcompensation frequency (30 Hz) may be generated by inserting a holdingframe between two adjacent writing frames of the normal drivingfrequency (60 Hz). The third compensation frequency may be 15 Hz whichis generated by dividing the second compensation frequency by two. Thethird compensation frequency (15 Hz) may be generated by inserting threeholding frames between two adjacent writing frames of the normal drivingfrequency (60 Hz). The fourth compensation frequency may be 7.5 Hz whichis generated by dividing the third compensation frequency by two. Thefourth compensation frequency (7.5 Hz) may be generated by insertingseven holding frames between two adjacent writing frames of the normaldriving frequency (60 Hz). The fifth compensation frequency may be 3.75Hz which is generated by dividing the fourth compensation frequency bytwo. The fifth compensation frequency (3.75 Hz) may be generated byinserting fifteen holding frames between two adjacent writing frames ofthe normal driving frequency (60 Hz). The sixth compensation frequencymay be 1.875 Hz which is generated by dividing the fifth compensationfrequency by two. The sixth compensation frequency (1.875 Hz) may begenerated by inserting thirty one holding frames between two adjacentwriting frames of the normal driving frequency (60 Hz). When the lowdriving frequency is 1 Hz, 0.9375 Hz which is determined by dividing thesixth compensation frequency by two is less than the low drivingfrequency of 1 Hz so that 0.9375 Hz is not decided as the compensationfrequency.

Referring to FIGS. 8A and 8B, the driving controller 200 receives theinput image data IMG (operation S10). The driving controller 200determines whether the input image data IMG represents the static imageor the video image (operation S20).

When the input image data IMG represents the video image, the drivingcontroller 200 may drive the display panel 100 in the normal drivingfrequency (operation S30).

When the input image data IMG represents the static image, the drivingcontroller 200 determines the low driving frequency corresponding to theinput image data IMG (operation S40). The low driving frequency may bethe minimum frequency in which the flicker does not occur when thestatic image is displayed. The low driving frequency may be variedaccording to the input image data IMG. For example, the low drivingfrequency may be determined based on difference between luminance ofprevious image data and luminance of present image data. For example,the low driving frequency may be determined based on the number ofpixels where the grayscale value is changed from the previous image datato the present image data.

After the low driving frequency is determined, the driving controller200 drives the display panel 100 in the first driving frequency(operation S50). The first driving frequency may be the normal drivingfrequency. The normal driving frequency may be the input frequency ofthe input image data IMG. For example, the plurality of the firstcompensation frequency frames (e.g., three in FIG. 9 ) having the firstcompensation frequency may be inserted in the operation S50.

When the display panel 100 is driven in the first compensation frequencyand the image transition of the input image data IMG occurs (operationS60), the driving controller 200 may determine whether the transitedinput image data IMG represents the static image or the video image(operation S20).

When the display panel 100 is driven in the first compensation frequencyand the image transition of the input image data IMG does not occur, thedriving controller 200 may generate the second compensation frequency bydividing the first compensation frequency into the parameter.

The driving controller 200 determines whether the second compensationfrequency is equal to or less than the low driving frequency or not(operation S70). When the second compensation frequency is equal to orless than the low driving frequency, the display panel is not driven inthe second compensation frequency but driven in the low drivingfrequency (operation S80). When the display panel 100 is driven in thelow driving frequency and the image transition of the input image dataIMG occurs (operation S90), the driving controller 200 may determinewhether the transited input image data IMG represents the static imageor the video image (operation S20). When the display panel 100 is drivenin the low driving frequency and the image transition of the input imagedata IMG does not occur, the display panel 100 may be driven in the lowdriving frequency.

When the second compensation frequency is greater than the low drivingfrequency, the driving controller 200 drives the display panel 100 inthe second compensation frequency (operation S100). For example, theplurality of the second compensation frequency frames (e.g. three inFIG. 9 ) having the second compensation frequency may be inserted in theoperation S100.

When the display panel 100 is driven in the second compensationfrequency and the image transition of the input image data IMG occurs(operation S110), the driving controller 200 may determine whether thetransited input image data IMG represents the static image or the videoimage (operation S20).

When the display panel 100 is driven in the second compensationfrequency and the image transition of the input image data IMG does notoccur, the driving controller 200 may generate the third compensationfrequency by dividing the second compensation frequency into theparameter.

The driving controller 200 determines whether the third compensationfrequency is equal to or less than the low driving frequency or not(operation S120). When the third compensation frequency is equal to orless than the low driving frequency, the display panel is not driven inthe third compensation frequency but driven in the low driving frequency(operation S80). When the display panel 100 is driven in the low drivingfrequency and the image transition of the input image data IMG occurs(operation S90), the driving controller 200 may determine whether thetransited input image data IMG represents the static image or the videoimage (operation S20). When the display panel 100 is driven in the lowdriving frequency and the image transition of the input image data IMGdoes not occur, the display panel 100 may be driven in the low drivingfrequency.

When the third compensation frequency is greater than the low drivingfrequency, the driving controller 200 drives the display panel 100 inthe third compensation frequency (operation S130). For example, theplurality of the third compensation frequency frames (e.g. three in FIG.9 ) having the third compensation frequency may be inserted in theoperation S130.

When the display panel 100 is driven in the third compensation frequencyand the image transition of the input image data IMG occurs (operationS140), the driving controller 200 may determine whether the transitedinput image data IMG represents the static image or the video image(operation S20).

When the display panel 100 is driven in the third compensation frequencyand the image transition of the input image data IMG does not occur, thedriving controller 200 may generate the fourth compensation frequency bydividing the third compensation frequency into the parameter.

The driving controller operates operations S150 to S170 in away same asthe operations S120 to S140. Until the compensation frequency generatedby dividing the previous compensation frequency by the parameter isequal to or less than the low driving frequency, the display panel 100is repetitively driven in the compensation frequency.

According to some example embodiments, the plurality of the compensationfrequency frames having each of the compensation frequencies may beinserted. For example, the plurality of first compensation frequencyframe having the first compensation frequency may be inserted and theplurality of second compensation frequency frame having the secondcompensation frequency may be inserted.

In FIG. 9 , three first compensation frequency frames having the firstcompensation frequency (e.g., 60 Hz) are inserted, three secondcompensation frequency frames having the second compensation frequency(e.g., 30 Hz) are inserted and three third compensation frequency frameshaving the third compensation frequency (e.g., 15 Hz) are inserted.Although the number of the first compensation frequency frames, thenumber of the second compensation frequency frames and the number of thethird compensation frequency frames are same as each other in FIG. 9 ,the present inventive concept is not limited thereto. Alternatively, thenumber of the first compensation frequency frames may be greater thanthe number of the second compensation frequency frames and the number ofthe second compensation frequency frames may be greater than the numberof the third compensation frequency frames. The number of thecompensation frequency frames may be properly adjusted to effectivelyprevent the flicker.

According to some example embodiments, the plurality of the compensationfrequency frames may be inserted prior to the low driving frequencyframe in the low frequency driving mode so that the afterimage of theprevious image or the flicker due to the hysteresis characteristics ofthe pixel switching elements may be prevented.

The flicker of the display panel 100 is prevented in the low frequencydriving mode so that the power consumption of the display apparatus maybe reduced and the display quality of the display panel 100 may beenhanced.

FIG. 10 is a table illustrating compensation frequencies for driving adisplay panel according to some example embodiments of the presentinventive concept. FIG. 11 is a flowchart diagram illustrating a methodof driving the display panel of FIG. 10 .

The display apparatus and the method of driving the display panelaccording to some example embodiments is substantially the same as thedisplay apparatus and the method of driving the display panel of theprevious example embodiments explained referring to FIGS. 1 to 9 exceptfor the method of determining the compensation frequency. Thus, the samereference numerals will be used to refer to the same or like parts asthose described in the previous example embodiments of FIGS. 1 to 9 andsome repetitive explanation concerning the above elements may beomitted.

Referring to FIGS. 1 to 4 and 9 to 11 , the display apparatus includes adisplay panel 100 and a display panel driver. The display panel driverincludes a driving controller 200, a gate driver 300, a gamma referencevoltage generator 400, a data driver 500 and an emission driver 600.

The display panel 100 includes a plurality of the pixels. Each pixelincludes an organic light emitting element OLED.

The pixel receives a data write gate signal GWP and GWN, a datainitialization gate signal GI, an organic light emitting elementinitialization signal GB, the data voltage VDATA and the emission signalEM and the organic light emitting element OLED of the pixel emits lightcorresponding to the level of the data voltage VDATA to display theimage.

The display panel 100 may be driven in a normal driving mode in whichthe display panel 100 is driven in a normal driving frequency and in alow frequency driving mode in which the display panel 100 is driven in afrequency less than the normal driving frequency.

The driving controller 200 may determine the low driving frequencycorresponding to the input image data IMG in the low frequency drivingmode. The driving controller 200 may determine a plurality ofcompensation frequencies greater than the low driving frequency. Thedriving controller 200 inserts a plurality of compensation frequencyframes having the compensation frequencies prior to a low drivingfrequency frame having the low driving frequency.

The driving controller 200 may generate the compensation frequencies byrepetitively multiplying a parameter to the low driving frequency.

In FIG. 9 , the normal driving frequency may be 60 Hz, the low drivingfrequency may be 1 Hz and the parameter may be two. The sixthcompensation frequency may be 2 Hz which is generated by multiplying twoto the low driving frequency. The sixth compensation frequency (2 Hz)may be generated by inserting twenty nine holding frames between twoadjacent writing frames of the normal driving frequency (60 Hz). Thefifth compensation frequency may be 4 Hz which is generated bymultiplying two to the sixth driving frequency. The fifth compensationfrequency (4 Hz) may be generated by inserting fourteen holding framesbetween two adjacent writing frames of the normal driving frequency (60Hz). The fourth compensation frequency may be 7.5 Hz approximate to 8 Hzwhich is generated by multiplying two to the fifth driving frequency. 8Hz cannot be obtained by inserting an integer number of holding framesbetween two adjacent writing frames of the normal driving frequency (60Hz) so that the fourth compensation frequency may be 7.5 Hz approximateto 8 Hz. The fourth compensation frequency (7.5 Hz) may be generated byinserting seven holding frames between two adjacent writing frames ofthe normal driving frequency (60 Hz). The third compensation frequencymay be 15 Hz which is generated by multiplying two to the fourth drivingfrequency. The third compensation frequency (15 Hz) may be generated byinserting three holding frames between two adjacent writing frames ofthe normal driving frequency (60 Hz). The second compensation frequencymay be 30 Hz which is generated by multiplying two to the third drivingfrequency. The second compensation frequency (30 Hz) may be generated byinserting a holding frame between two adjacent writing frames of thenormal driving frequency (60 Hz). The first compensation frequency maybe 60 Hz which is generated by multiplying two to the second drivingfrequency. The first compensation frequency (60 Hz) may be the normaldriving frequency (60 Hz). A subsequent candidate compensation frequencymay be 120 Hz which is generated by multiplying two to the first drivingfrequency is greater than the normal driving frequency so that 120 Hz isnot decided as the compensation frequency.

Referring to FIG. 11 , the driving controller 200 receives the inputimage data IMG (operation S10). The driving controller 200 determineswhether the input image data IMG represents the static image or thevideo image (operation S20).

When the input image data IMG represents the video image, the drivingcontroller 200 may drive the display panel 100 in the normal drivingfrequency (operation S30).

When the input image data IMG represents the static image, the drivingcontroller 200 determines the low driving frequency corresponding to theinput image data IMG and generates the compensation frequency bymultiplying the parameter to the low driving frequency (operation S40).The driving controller 200 may repetitively generate the compensationfrequencies which are less than the normal driving frequency bymultiplying the parameter to the low driving frequency.

After the low driving frequency and the compensation frequencies aredetermined, the driving controller 200 drives the display panel 100 in afirst compensation frequency (operation S50).

When the display panel 100 is driven in the first compensation frequencyand the image transition of the input image data IMG occurs (operationS60), the driving controller 200 may determine whether the transitedinput image data IMG represents the static image or the video image(operation S20).

When the display panel 100 is driven in the first compensation frequencyand the image transition of the input image data IMG does not occur, thedriving controller 200 drives the display panel 100 in a secondcompensation frequency (operation S70).

When the display panel 100 is driven in the second compensationfrequency and the image transition of the input image data IMG occurs(operation S80), the driving controller 200 may determine whether thetransited input image data IMG represents the static image or the videoimage (operation S20).

When the display panel 100 is driven in the second compensationfrequency and the image transition of the input image data IMG does notoccur, the driving controller 200 drives the display panel 100 in athird compensation frequency.

When the display panel 100 is driven in the third compensation frequencyand the image transition of the input image data IMG occurs, the drivingcontroller 200 may determine whether the transited input image data IMGrepresents the static image or the video image (operation S20).

The driving controller 200 repetitively operate the compensationfrequency driving in a way same as operations S70 and S80. In the sameway, the driving controller 200 may drive the display panel 100 in thesixth compensation frame.

When the display panel 100 is driven in the sixth compensation frequencyand the image transition of the input image data IMG occurs (operationS100), the driving controller 200 may determine whether the transitedinput image data IMG represents the static image or the video image(operation S20).

When the display panel 100 is driven in the sixth compensation frequencyand the image transition of the input image data IMG does not occur, thedriving controller 200 drives the display panel 100 in the low drivingfrequency (operation S110).

When the display panel 100 is driven in the low driving frequency andthe image transition of the input image data IMG occurs (operationS120), the driving controller 200 may determine whether the transitedinput image data IMG represents the static image or the video image(operation S20). When the display panel 100 is driven in the low drivingfrequency and the image transition of the input image data IMG does notoccur, the display panel 100 is driven in the low driving frequency

According to some example embodiments, the plurality of the compensationfrequency frames may be inserted prior to the low driving frequencyframe in the low frequency driving mode so that instances of anafterimage of the previous image or the flicker due to the hysteresischaracteristics of the pixel switching elements may be prevented orreduced.

The flicker of the display panel 100 is prevented or reduced in the lowfrequency driving mode so that the power consumption of the displayapparatus may be reduced and the display quality of the display panel100 may be enhanced.

FIG. 12 is a flowchart diagram illustrating a method of driving adisplay panel 100 according to some example embodiments of the presentinventive concept when a low driving frequency is 1 Hz.

The display apparatus and the method of driving the display panelaccording to some example embodiments is substantially the same as thedisplay apparatus and the method of driving the display panel of theprevious example embodiments explained referring to FIGS. 1 to 9 exceptfor the method of determining the compensation frequency. Thus, the samereference numerals will be used to refer to the same or like parts asthose described in the previous example embodiments of FIGS. 1 to 9 andsome repetitive explanation concerning the above elements may beomitted.

Referring to FIGS. 1 to 4 and 12 , the display apparatus includes adisplay panel 100 and a display panel driver. The display panel driverincludes a driving controller 200, a gate driver 300, a gamma referencevoltage generator 400, a data driver 500 and an emission driver 600.

The display panel 100 includes a plurality of the pixels. Each pixelincludes an organic light emitting element OLED.

The pixel receives a data write gate signal GWP and GWN, a datainitialization gate signal GI, an organic light emitting elementinitialization signal GB, the data voltage VDATA and the emission signalEM and the organic light emitting element OLED of the pixel emits lightcorresponding to the level of the data voltage VDATA to display theimage.

The display panel 100 may be driven in a normal driving mode in whichthe display panel 100 is driven in a normal driving frequency and in alow frequency driving mode in which the display panel 100 is driven in afrequency less than the normal driving frequency.

The driving controller 200 may determine the low driving frequencycorresponding to the input image data IMG in the low frequency drivingmode. The driving controller 200 may determine a plurality ofcompensation frequencies greater than the low driving frequency. Thedriving controller 200 inserts a plurality of compensation frequencyframes having the compensation frequencies prior to a low drivingfrequency frame having the low driving frequency.

According to some example embodiments, the compensation frequency frameshaving at least two compensation frequencies may be repetitivelyinserted until a predetermined count is satisfied.

For example, when the repetitive compensation frequency frames are acompensation frequency frame of 60 Hz and a compensation frequency frameof 30 Hz and the predetermined count is three, the compensationfrequency frames may be inserted in a sequence of 60 Hz, 30 Hz, 60 Hz,30 Hz, 60 Hz, 30 Hz, 15 Hz, 7.5 Hz, 3.75 Hz and 1.875 Hz.

The repetitive compensation frequency frames and the predetermined countmay be set to prevent the flicker of the display panel 100. Therepetitive compensation frequency frames and the predetermined count maybe adjusted according to the input image data IMG.

According to some example embodiments, the plurality of the compensationfrequency frames may be inserted prior to the low driving frequencyframe in the low frequency driving mode so that the afterimage of theprevious image or the flicker due to the hysteresis characteristics ofthe pixel switching elements may be prevented.

The flicker of the display panel 100 is prevented in the low frequencydriving mode so that the power consumption of the display apparatus maybe reduced and the display quality of the display panel 100 may beenhanced.

FIG. 13 is a flowchart diagram illustrating a method of driving adisplay panel 100 according to some example embodiments of the presentinventive concept when a low driving frequency is 1 Hz.

The display apparatus and the method of driving the display panelaccording to the present example embodiment is substantially the same asthe display apparatus and the method of driving the display panel of theprevious example embodiments explained referring to FIGS. 1 to 9 exceptfor the method of determining the compensation frequency. Thus, the samereference numerals will be used to refer to the same or like parts asthose described in the previous example embodiment of FIGS. 1 to 9 andsome repetitive explanation concerning the above elements may beomitted.

Referring to FIGS. 1 to 4 and 13 , the display apparatus includes adisplay panel 100 and a display panel driver. The display panel driverincludes a driving controller 200, a gate driver 300, a gamma referencevoltage generator 400, a data driver 500 and an emission driver 600.

The display panel 100 includes a plurality of the pixels. Each pixelincludes an organic light emitting element OLED.

The pixel receives a data write gate signal GWP and GWN, a datainitialization gate signal GI, an organic light emitting elementinitialization signal GB, the data voltage VDATA and the emission signalEM and the organic light emitting element OLED of the pixel emits lightcorresponding to the level of the data voltage VDATA to display theimage.

The display panel 100 may be driven in a normal driving mode in whichthe display panel 100 is driven in a normal driving frequency and in alow frequency driving mode in which the display panel 100 is driven in afrequency less than the normal driving frequency.

The driving controller 200 may determine the low driving frequencycorresponding to the input image data IMG in the low frequency drivingmode. The driving controller 200 may determine a plurality ofcompensation frequencies greater than the low driving frequency. Thedriving controller 200 inserts a plurality of compensation frequencyframes having the compensation frequencies prior to a low drivingfrequency frame having the low driving frequency.

According to some example embodiments, the compensation frequency frameshaving at least two compensation frequencies may be repetitivelyinserted until a condition (e.g., a predetermined condition) issatisfied.

For example, when the repetitive compensation frequency frames are acompensation frequency frame of 60 Hz and a compensation frequency frameof 30 Hz and the condition (e.g., the predetermined condition) issatisfied in two repetition, the compensation frequency frames may beinserted in a sequence of 60 Hz, 30 Hz, 60 Hz, 30 Hz, 15 Hz, 7.5 Hz,3.75 Hz and 1.875 Hz.

The repetitive compensation frequency frames and the condition (e.g.,the predetermined condition) may be set to prevent the flicker of thedisplay panel 100. The repetitive compensation frequency frames and thecondition (e.g., the predetermined condition) may be adjusted accordingto the input image data IMG.

According to some example embodiments, the plurality of the compensationfrequency frames may be inserted prior to the low driving frequencyframe in the low frequency driving mode so that the afterimage of theprevious image or the flicker due to the hysteresis characteristics ofthe pixel switching elements may be prevented.

The flicker of the display panel 100 is prevented or reduced in the lowfrequency driving mode so that the power consumption of the displayapparatus may be reduced and the display quality of the display panel100 may be enhanced.

FIG. 14 is a circuit diagram illustrating a pixel of a display panel 100according to some example embodiments of the present inventive concept.FIG. 15 is a timing diagram illustrating input signals applied to thepixel of FIG. 14 .

The display apparatus and the method of driving the display panelaccording to the present example embodiment is substantially the same asthe display apparatus and the method of driving the display panel of theprevious example embodiment explained referring to FIGS. 1 to 9 exceptfor the structure of the pixel. Thus, the same reference numerals willbe used to refer to the same or like parts as those described in theprevious example embodiment of FIGS. 1 to 9 and some repetitiveexplanation concerning the above elements may be omitted.

Referring to FIGS. 1, 4 to 9, 14 and 15 , the display apparatus includesa display panel 100 and a display panel driver. The display panel driverincludes a driving controller 200, a gate driver 300, a gamma referencevoltage generator 400, a data driver 500, and an emission driver 600.

The display panel 100 includes a plurality of the pixels. Each pixelincludes an organic light emitting element OLED.

The pixel receives a data write gate signal GWP and GWN, a datainitialization gate signal GI, an organic light emitting elementinitialization signal GB, the data voltage VDATA and the emission signalEM and the organic light emitting element OLED of the pixel emits lightcorresponding to the level of the data voltage VDATA to display theimage.

According to some example embodiments, the pixel may include a switchingelement of a first type and a switching element of a second typedifferent from the first type. For example, the switching element of thefirst type may be a polysilicon thin film transistor. For example, theswitching element of the first type may be a low temperature polysilicon(LTPS) thin film transistor. For example, the switching element of thesecond type may be an oxide thin film transistor. For example, theswitching element of the first type may be a P-type transistor and theswitching element of the second type may be an N-type transistor.

At least one of the pixels may include first to seventh pixel switchingelements T1 to T7, a storage capacitor CST and the organic lightemitting element OLED.

According to some example embodiments, the seventh pixel switchingelement T7 includes a control electrode to which the organic lightemitting element initialization gate signal GB is applied, an inputelectrode to which the initialization voltage VI is applied and anoutput electrode connected to the anode electrode of the organic lightemitting element OLED.

For example, the seventh pixel switching element T7 may be thepolysilicon thin film transistor. For example, the seventh pixelswitching element T7 may be a P-type thin film transistor.

In FIG. 15 , during a first duration DU1, the first node N1 and thestorage capacitor CST are initialized in response to the datainitialization gate signal GI. During a second duration DU2, a thresholdvoltage |VTH| of the first pixel switching element T1 is compensated andthe data voltage VDATA of which the threshold voltage |VTH| iscompensated is written to the first node N1 in response to the first andsecond data write gate signals GWP and GWN. During a third duration DU3,the anode electrode of the organic light emitting element OLED isinitialized in response to the organic light emitting elementinitialization gate signal GB. During a fourth duration DU4, the organiclight emitting element OLED emit the light in response to the emissionsignal EM so that the display panel 100 displays the image.

According to some example embodiments, the active level of the organiclight emitting element initialization signal GB may be a low level.

According to some example embodiments, some of the pixel switchingelements may be designed using the oxide thin film transistors.According to some example embodiments, the third pixel switching elementT3 and the fourth pixel switching element T4 may be the oxide thin filmtransistors. The first pixel switching element T1, the second pixelswitching element T2, the fifth pixel switching element T5, the sixthpixel switching element T6 and the seventh pixel switching element T7may be the polysilicon thin film transistors.

The display panel 100 may be driven in a normal driving mode in whichthe display panel 100 is driven in a normal driving frequency and in alow frequency driving mode in which the display panel 100 is driven in afrequency less than the normal driving frequency.

The driving controller 200 may determine the low driving frequencycorresponding to the input image data IMG in the low frequency drivingmode. The driving controller 200 may determine a plurality ofcompensation frequencies greater than the low driving frequency. Thedriving controller 200 inserts a plurality of compensation frequencyframes having the compensation frequencies prior to a low drivingfrequency frame having the low driving frequency.

According to some example embodiments, the plurality of the compensationfrequency frames may be inserted prior to the low driving frequencyframe in the low frequency driving mode so that the afterimage of theprevious image or the flicker due to the hysteresis characteristics ofthe pixel switching elements may be prevented.

The flicker of the display panel 100 is prevented or reduced in the lowfrequency driving mode so that the power consumption of the displayapparatus may be reduced and the display quality of the display panel100 may be enhanced.

According to some example embodiments of the present inventive conceptas explained above, the power consumption of the display apparatus maybe reduced and the display quality of the display panel may be enhanced.

The foregoing is illustrative of the present inventive concept and isnot to be construed as limiting thereof. Although a few exampleembodiments of the present inventive concept have been described, thoseskilled in the art will readily appreciate that many modifications arepossible in the example embodiments without materially departing fromthe novel teachings and aspects of the present inventive concept.Accordingly, all such modifications are intended to be included withinthe scope of the present inventive concept as defined in the claims. Inthe claims, means-plus-function clauses are intended to cover thestructures described herein as performing the recited function and notonly structural equivalents but also equivalent structures. Therefore,it is to be understood that the foregoing is illustrative of the presentinventive concept and is not to be construed as limited to the specificexample embodiments disclosed, and that modifications to the disclosedexample embodiments, as well as other example embodiments, are intendedto be included within the scope of the appended claims. The presentinventive concept is defined by the following claims, with equivalentsof the claims to be included therein.

What is claimed is:
 1. A method of driving a display panel, the methodcomprising: displaying a first static image in a first low drivingfrequency during a first period; displaying a second static image in aplurality of compensation frequencies during a second period; anddisplaying the second static image in a second low driving frequencyduring a third period, wherein a video image is displayed on the displaypanel in a normal driving frequency, wherein the first low drivingfrequency is less than the normal driving frequency, wherein the secondlow driving frequency is less than the normal driving frequency, whereinthe compensation frequencies are greater than the second low drivingfrequency, wherein the compensation frequencies comprise at least twodifferent frequencies, wherein the display panel comprises a pixelcomprising an N-type transistor and a P-type transistor, and wherein theN-type transistor is driven in the first and second low drivingfrequencies when the first and second static images are displayed on thedisplay panel.
 2. The method of claim 1, wherein the pixel furthercomprises: a first pixel switching element comprising a controlelectrode connected to a first node, an input electrode connected to asecond node and an output electrode connected to a third node; a secondpixel switching element comprising a control electrode configured toreceive a first data write gate signal, an input electrode configured toreceive a data voltage, and an output electrode connected to the secondnode; a third pixel switching element comprising a control electrodeconfigured to receive a second data write gate signal, an inputelectrode connected to the first node, and an output electrode connectedto the third node; and an organic light emitting element configured toemit light based on a high power voltage, a low power voltage and acurrent flowing through the first pixel switching element.
 3. The methodof claim 2, wherein the pixel further comprises: a fourth pixelswitching element comprising a control electrode configured to receive adata initialization gate signal, an input electrode configured toreceive an initialization voltage, and an output electrode connected tothe first node.
 4. The method of claim 3, wherein the pixel furthercomprises: a fifth pixel switching element comprising a controlelectrode configured to receive an emission signal, an input electrodeconfigured to receive the high power voltage, and an output electrodeconnected to the second node; a sixth pixel switching element comprisinga control electrode configured to receive the emission signal, an inputelectrode connected to the third node and an output electrode connectedto an anode electrode of the organic light emitting element; and aseventh pixel switching element comprising a control electrodeconfigured to receive an organic light emitting element initializationgate signal, an input electrode configured to receive the initializationvoltage, and an output electrode connected to the anode electrode of theorganic light emitting element.
 5. The method of claim 4, wherein thepixel further comprises: a storage capacitor comprising a firstelectrode configured to receive the high power voltage, and a secondelectrode connected to the first node, wherein the organic lightemitting element comprises a cathode electrode configured to receive thelow power voltage.
 6. The method of claim 5, wherein the first pixelswitching element, the second pixel switching element, the fifth pixelswitching element and the sixth pixel switching element comprisepolysilicon thin film transistors, and wherein the third pixel switchingelement, the fourth pixel switching element, and the seventh pixelswitching element comprise oxide thin film transistors.
 7. The method ofclaim 5, wherein the first pixel switching element, the second pixelswitching element, the fifth pixel switching element and the sixth pixelswitching element comprise P-type transistors, and wherein the thirdpixel switching element, the fourth pixel switching element, and theseventh pixel switching element comprise N-type transistors.
 8. Themethod of claim 1, wherein the compensation frequencies graduallydecrease during the second period.
 9. The method of claim 1, wherein thecompensation frequencies comprise a first compensation frequency and asecond compensation frequency less than the first compensationfrequency, and wherein a first compensation frequency frame having thefirst compensation frequency is inserted prior to a second compensationfrequency frame having the second compensation frequency during thesecond period.
 10. The method of claim 1, wherein the compensationfrequencies comprise a first compensation frequency and a secondcompensation frequency less than the first compensation frequency,wherein a plurality of first compensation frequency frames having thefirst compensation frequency are located in the second period, andwherein a plurality of second compensation frequency frames having thesecond compensation frequency are located in the second period.
 11. Themethod of claim 1, wherein a plurality of compensation frequency frameshaving the at least two different frequencies are repetitively locatedin the second period until a predetermined count is satisfied.
 12. Themethod of claim 1, wherein a plurality of compensation frequency frameshaving the at least two different frequencies are repetitively locatedin the second period until a predetermined condition is satisfied. 13.The method of claim 1, wherein the compensation frequencies aregenerated by repetitively dividing the normal driving frequency by aparameter.
 14. The method of claim 13, wherein the normal drivingfrequency is determined as a first compensation frequency, wherein asecond compensation frequency is determined by dividing the normaldriving frequency by the parameter when a result of dividing the normaldriving frequency by the parameter is greater than the second lowdriving frequency, and wherein a third compensation frequency isdetermined by dividing the second compensation frequency by theparameter when a result of dividing the second compensation frequency bythe parameter is greater than the second low driving frequency.
 15. Themethod of claim 1, wherein the compensation frequencies are generated byrepetitively multiplying a parameter by the second low drivingfrequency.
 16. The method of claim 15, wherein an N-th compensationfrequency is determined by multiplying the parameter by the second lowdriving frequency when the N-th compensation frequency a result ofmultiplying the parameter by the second low driving frequency is lessthan the normal driving frequency, wherein an (N−1)-th compensationfrequency is determined by multiplying the parameter by the N-thcompensation frequency when a result of multiplying the parameter of theN-th compensation frequency is less than the normal driving frequency,and wherein N is a natural number equal to or greater than two.